Immunomodulatory Effects of Different Lactic Acid Bacteria on Allergic Response and Its Relationship with In Vitro Properties

Abstract

Some studies reported that probiotic could relieve allergy-induced damage to the host, but how to get a useful probiotic is still a challenge. In this study, the protective effects of three lactic acid bacteria (La, Lp and Lc) were evaluated in a mouse model, and its relationship with the in vitro properties was analyzed. The in vitro results indicated that La with the capacity to inhibit IL-4 production could have a better anti-allergy effect in vivo than two others. However, the animal trials showed that all LAB strains could alleviate allergen-induced airway inflammation. Among them, LAB strain Lp had a better effect in inhibiting allergic response through a modulation of Th1/Th2 balance and an increase of regulatory T cells. This difference could be explained by that different LAB strains have a strain-specific effect on gut microbiota closely associated with host immune responses. Finally, this study did not only obtain an effective anti-allergy probiotic strain via animal study, but also indicate that probiotic-induced effect on intestinal microbiota should be considered as an important screening index, apart from its inherent characteristics.

Fig 1. Protocol of mice experiment.

Mice were orally administrated with 200 μL/day of bacterial suspension or PBS until mice were sacrificed. At weeks 2, 3 and 4, mice underwent intraperitoneal injection with a mixture of Der p2/Alum or PBS (◆) at weekly intervals. To induce allergic airway inflammation, all mice were inhalation challenged with HDM allergen after the last vaccination.

Fig 2. Immunomodulatory properties of different LAB strains in vitro.

The levels (pg/mL) of IFN-γ (A), IL-12 (B), IL-4 (C) and IL-10 (D) were measured by ELISA.

Fig 3. Effects of different LAB strains on antibodies in serum.

The levels of total IgE (A) and Der p2-specific IgE (B), IgG2a (C) and IgG1 (D) in serum were respectively measured as ng/mL or optical density (OD) by ELISA. ^*P < 0.05 vs control group.

Fig 4. Effects of different LAB strains on cytokines production in serum.

The levels of IFN-γ (A), IL-4 (B) and the ratio of IFN-γ/IL-4 (C) were measured by ELISA. ^*P < 0.05 vs positive group, ^#P < 0.05 vs La group.

Fig 5. Histological analysis of the lung tissues from positive, Lc, La, Lp, and control group.

The bar length was 100 μm and the magnification times was 200.

Fig 6. Analysis of inflammatory responses after inhalation challenge.

The level of IL-4 (A) in the BALF was measured by ELISA. The mRNA level of Foxp3 (B) in the lung tissues was analyzed by RT-PCR. ^#P < 0.05 vs control group and ^*P < 0.05 vs positive group.

Fig 7

Effects of different LAB strains on the levels of CD4⁺CD25⁺Foxp3⁺ Tregs in the spleen (A) and MLN (B) of Der p2-sensitized mice. ^*P < 0.05 vs positive group and ^#P < 0.05 vs La group.

Fig 8. PCR-DGGE analysis of fecal bacteria species composition.